[quote author=Rfg4retir]Thx again, yeah my guess is that it has sat for a yr now[/quote]
Depending on where it was stored, there may not be an issue. But, if you buy it and drive away, I'd have a couple of spare filters on hand. Depending on the coach/layout, it might be easy to get to the primary fuel filter. Usually, it's a Racor filter which also removes water from the fuel (there'll be a drain on the bottom of the filter to drain out the trapped water).
Adding biocide to a fuel tank that already has algae growth doesn't hurt. Similar to chlorine added to a swimming pool, you "shock" it with a higher dose (read the instructions on the container). It will kill the existing algae, but you could still experience a clogged filter from the dead stuff being trapped in the filter.
For clarification, the issue with algae getting past the filters is that it can clog the injectors ($$). But the 2-step filtration (primary and secondary filters) will usually prevent that.